Lighting fixtures or luminaires are typically made from cast aluminum housings. Cast aluminum housings are used to dissipate heat that is generated by the light source and the power supply to energize that source. In the case of light-emitting diode (LED) lighting fixtures, it is extremely important and imperative that the junction temperature of the LED is maintained within the temperatures that are reported in LM80 data supplied by the LED manufacturer. If the temperature is not maintained and exceeds the allowable threshold, the life of the LED diminishes substantially, the color characteristics can change, and the lumen output decreases.
Existing cast aluminum fixtures are a good solution for dissipating heat because aluminum has very good thermal conductive properties that transfer the heat away from the LED light engine to maintain a desired junction temperature of the LED. While this aluminum housing is good at heat dissipation, it is not very good at corrosion resistance, has design limitations, and is heavy.
Poorly designed aluminum heat sink housings with the use of higher power LEDs can create many of these problems.
Corrosion is a significant issue and a problem for aluminum lighting fixtures. There have been advances made in coating aluminum fixtures to help against corrosion which include expensive multi-stage coatings but these are still susceptible to corrosion in environments that have salt and other types of chemicals and contaminants especially if the coating is chipped. These coatings and the aluminum fixture can easily deteriorate from both the outside and the inside of the fixture which does not have a protective coating. Another disadvantage of the aluminum LED fixture housing is material cost and the need to perform secondary operations for assembly.
Thus, there is a need for a luminaire that is corrosion resistant and yet solves the existing issues with aluminum LED fixtures including high cost and high weight.
Furthermore, fire and explosions are a major safety concern in manufacturing plants and other industrial facilities. There are regulatory bodies such as the Occupational Safety and Health Administration (OSHA) that have established systems that classify locations which exhibit potentially dangerous conditions to the degree of hazard presented. OSHA Publication 3073 defines a “hazardous location” as “areas where flammable liquids, gases or vapors or combustible dusts exist in sufficient quantities to produce an explosion or fire.” Suitable equipment must be used in hazardous locations to protect against the explosive and flammable potential of these substances.
The National Electrical Code (NEC) and the Canadian Electrical Code (CEC) defines a “hazardous area” as “[a]n area where a potential hazard (e.g., a fire, an explosion, etc.) may exist under normal or abnormal conditions because of the presence of flammable gases or vapors, combustible dusts or ignitable fibers or flyings.” Thus, there is a need for a corrosion resistant luminaire that is rated for use in hazardous locations and/or is rated as explosion proof according to UL classifications (Class 1, Division 1 and 2 and Class 2, Divisions 1 and 2).
There is also a need for a corrosion resistant luminaire that solves the above issues but also has increased ability to dissipate the heat from higher lumen output.